The liver is commonly involved in patients with AIDS and a first line investigation for hepatic dysfunction is liver ultrasound (US) which is often abnormal. It is unclear how these US abnormalities correlate with the underlying pathological processes. A retrospective study was performed in 48 patients with HIV disease who had undergone both liver biopsy and hepatic (US), correlating the findings. Only 25% of patients had an entirely normal liver (US) examination and only 10% patients had a normal liver biopsy. The commonest sonographic abnormalities was a diffusely hyperechoic liver seen in 46% of patients and this correlated with steatosis. Forty-four percent of biopsies contained more than one histological abnormality including granulomas, inflammation, steatosis or siderosis. In addition clinically unsuspected pathology was revealed in five of the cases of mycobacterial infection and in three cases of lymphoma. The combination of multiple histological abnormalities, unsuspected pathology, and the altered immune response in this group makes the US findings even less specific than in non-AIDS patients. We recommend that liver biopsy should remain an essential and early part of the management of AIDS patients.